MFC是Application Framework， 而不仅仅是一个Class Library。

Application Framework is an extended collection of classes that cooperate to support a complete application
architecture or application model, providing more complete application development
support than a simple set of class libraries.

能够被称为Framework者，必须其中的类别特性紧密咬合，互相呼应。Class与Class之间的关系，是MFC区别于普通Class Library最重要的一点。